Our investigation is focused on the understanding of electrical aging in polymeric materials under 50 Hz ac voltage. In this report, a needle electrode molded into the insulant to simulate defects producing local field enhancement is used. Special emphasis is given to low density polyethylene. The transition between the discharge-free electroluminescent state to micropartial discharge (PD) state (...
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Measurements of thermally stimulated currents were made on ionomer/polyethylene blends. The objective of this work was to study space charge formation in these materials. Two ionomers were compared; both ionomers contained methacrylic acid, neutralized by zinc in one and by sodium in the other. A large current peak centered near 60°C was observed in all blends and associated with the motion of...
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The ultra-high frequency (UHF) technique of partial discharge detection has been used to study the partial discharges produced by electrode protrusions and surface contamination in a gas insulated substation (GIS). The paper describes the stages of discharge development from inception to breakdown. The work has shown that the UHF technique may be used to identify distinct phases of discharge activ...
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The conduction process in polyetheretherketone (PEEK) is discussed mainly from the results of dc conduction, thermal pulse current (TPC), thermally stimulated current (TSC), and pulsed electroacoustic (PEA) measurements. It was found that dc conduction currents in PEEK are consistent with the values predicted by a theory based on the conventional thermally activated ionic hopping process. The ioni...
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Contrary to the Debye's theory of a distribution of relaxation times, the logarithm of the relaxation current plotted as function of time has several nearly straight sections of decreasing slopes. The slopes formed short series having common geometrical ratios of ~2, 1.5, and 1.2. The ratios represent stepped changes of the probability of charge carrier excitation, generally caused by the stepped ...
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HV, applied to a point cathode (radius of curvature ~1 to ~8 μm) in a nonpolar liquid, brings about a regular current pulse regime above a threshold value Vs. This regime is similar to the Trichel pulse regime for corona in air. We present results of an investigation of this threshold voltage Vs in argon over a wide range of densities. In gaseous argon, the Vs(P...
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The dc electrical conduction in MI1M and MI1I2M composite specimens has been studied, where I1 is polyimide (PI) or polyester (PET), and I2 is a thin plasma deposited silicon compound film (oxide, P-SiO2, or nitride, P-SiN). The current-electric field (j(E,T)) characteristics have been measured over a wide range of E values (O&les;E...
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Considerable theoretical and experimental research on polluted insulators has yet to yield a perfect generalized mathematical model which can predict accurately critical flashover voltages and currents. In this paper an ac model has been proposed especially applicable to static arcs. The salient feature of the proposed model is that it takes into account the appropriate selection of arc constants ...
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Charged dielectrics can cause an electrostatic discharge (ESD) that damages electronic circuits because of the electromagnetic noise associated with the discharge. Newly developed anti-ESD polymers are expected to be `anti-ESD polymer insulating materials', but the mechanism of their action against ESD has not been explained. Since the anti-ESD polymers contain some kind of polymer solid electroly...
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The DC breakdown characteristics of a sphere-to-sphere gap with conducting objects supported by an insulator rod in atmospheric air are investigated experimentally to provide fundamental parameters determining the breakdown voltage in the presence of floating objects around DC power apparatus by an air insulation. The shape of tested floating objects made of metal is plate, needle or sphere. Exper...
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The dc and ac electrical conduction properties have been investigated in four composites containing hydroxyl-terminated polybutadiene (HTPB) as binder and different proportions of aluminum particles as filler in a temperature range of -60 to +70°C and a frequency range of 40 Hz to 100 kHz. A change in conduction mechanism at a temperature of 4±3°C was displayed explicitly in de meas...
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This paper presents the study of the major parameters on static electrification, using full-scale shell type transformers (570 MVA, 405 kV and 100 MVA, 500 kV). The consequences of static electrification on the dielectric strength and the conditions of partial discharge occurrence also are studied with oil flow rate up to 5 times the nominal value. It shows that the leakage currents are strongly i...
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Time-resolved pictures of discharges with simultaneous recording of predischarge currents have been obtained in different oil gaps under impulse voltage of positive polarity. It has been stated that in certain experimental conditions, a process similar to the leader process in air occurs, with the typical features of a leader channel and a streamer zone
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A semi-empirical model for high-field conduction in polyethylene is developed on the basis of data in the literature for ac conductivity in the range of 30 to 60 kV/mm and `charge injection' from a needle in the range of 160 kV/mm. The model is used to compute high-field conduction-related phenomena by solving Poisson's equation with field-dependent conductivity and time-dependent applied voltage ...
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The paper describes a technique for simulating the presence of partial discharges in gas-insulated substation (GIS) equipment. The technique employs a pulse generator to inject current pulses through a suitable protrusion. The current pulses have similar temporal characteristics to those produced by an actual discharge event, with the added advantage that their magnitudes can be controlled accurat...
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Electroluminescence associated with ac voltage aging of polyolefins has been reported under divergent field configuration. Neither the mechanism of excitation nor the nature of luminescent centers are well understood in these polymers. Homegeneous field experiments are desirable since they are easier to run and more light can be collected, thereby allowing spectral analysis to be made. We describe...
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The effect of filler concentration on the dielectric properties in the ultralow-frequency region and on the electrical conductivity was studied for ethylene propylene rubber. First, we investigated the relation between the electrical conductivity and filler concentration: as the volume fraction of fillers qa increased, the conductivity decreased in the low filler concentration region bu...
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Results of an investigation to clarify the process of surface flashover in gases are reported. Two hemispherical capped rods of 12 mm diameter, separated by a half-cylindrical spacer of 50 mm diameter, formed the samples. The spacer materials were polytetrafluoroethylene, acrylic and nylon. High-speed streak photographs of impulse flashover indicate that the presence of a spacer not only lowers th...
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The development of a user-friendly, interactive personal computer package for designing insulators to be used in polluted conditions is presented. This is accomplished by integrating a dynamic arc model that computes the pollution flashover voltage within the Microsoft Windows application program. Suspension, station post and pin type insulators of numerous shapes have been incorporated into the p...
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Aims & Scope

IEEE Transactions on Dielectrics and Electrical Insulation contains topics that are concerned with dielectric phenomena and measurements, with development and characterization of gaseous, vacuum, liquid and solid electrical insulating materials and systems; and with utilization of these materials in circuits and systems under condition of use.